Couplers

Last blog there was some details of fitting couplers into two of our BS cars at Newport. It has occurred to us that the arrangements were not well illustrated and readers of this blog may appreciate some better details of the process.

Just as well you asked!

In the repair shed X31 has just had its maintenance exam completed. It does though need attention to the drag box at the number 1 end. For this work to be undertaken the first thing to do is removed the coupler and draft assembly.

The coupler and assembly was removed on Saturday ready for welding repairs next week. ________________________________________________________________

We begin at the very beginning. Well that is not quite true as we have already removed the carry iron and the coupler is supported by a tie down strap. This was done a couple of weeks ago as part of the evaluation of the scope of repairs required._______________________________________________________________

Looking along the coupler shank from the outer end we can see there is a moderate gap between the yoke and the side of the drag box. The silver vertical highlights this area. The silver is the front face of the front follower of the package. The gap is around 12 mm and while that is not disastrous in a reconditioned state it will be around 3 mm. If it is fixed now the task will be quick, simple and cheap._____________________________________________________________

Now we are under the loco looking up at the draft assembly. The dish shaped carrying bracket with its four bolts are obvious. On the extreme right we can just see part of the draw pin that joins the coupler to the yoke. The front follower is a thick piece of steel plate running top to bottom about a quarter of the way from right to left._________________________________________________________

The photographer has swung around. Still looking up but this time the coupler shank is to the left with the cotter for the draw pin in place and the draft assembly to the right. The front follower is now prominent and it is possible to see a gap between the follower and the front cheeks of the drag box. There should be no gap here and we can also see the side gap at the front of the yoke. The front end of the drag box is the end that tends to get the most wear as this is the end subject to wear due to the pulling effect of the loco.___________________________________________________________________

So now we get ready with the engine crane attached to the coupler shank behind the head. With a bit of luck the coupler will be balanced.________________________________________________________________

The coupler is pulled forward part way. The uncoupling chain is still connected to the lifter as a safety measure. When we are confident that the lift is under control, the chain will be disconnected.___________________________________________________________________

The coupler is out and has been put on the ground. The first thing you might notice is the much shorter shank length compared to the couplers used in the carriages. As a rule, the longer the vehicle the longer the coupler shank which allows for side swing which is greater for longer vehicles.______________________________________________________________

The draft assembly has been lowered out of the drag box using the lifting table. There are no pictures as there is just not enough room to get in there with a camera while the lowering is happening. This is therefore the drag box without the draft assembly. We are looking up with the coupler end to the right. The front and rear cheeks can be seen with the wear marks where the followers rub against these faces.____________________________________________________________________

Repositioning a bit now looking towards the rear of the drag box with the rear cheeks and the wear marks prominent._______________________________________________________________

Now with the photographers back against the cowcatcher the front side face is shown. The sides have been worn and will be built either by pad welding where the thickness is restored by a lot of runs of weld or by having a piece of plate welded on.______________________________________________________________

Right up inside the drag box looking out where the coupler goes, the left side front cheek shows a lot of wear but only on the lower half. The side wear caused by the end of the front follower shows that the there has not been full contact between the follower and the drag box. In the restoration of the drag box the dimensions will be checked and the build up adjusted to ensure the correct matching surfaces.________________________________________________________

The right side has wear that is a bit more even but you can see at the lower edge there is some distortion. What do you think of the view of the track beyond the cowcatcher opening. There is a carriage to the right; which one is it?____________________________________________________________

A look at the front end of the draft assembly. The draw pin comes up from underneath. The front follower has some wear marks but they are not even. Of course we know that because the drag box is worn unevenly as well. Looking at the front follower where it enters the yoke, there is a tapered wear mark suggesting the assembly has been twisting somewhat in service. This has been possible because of the side wear noted in the second image of this blog.________________________________________________________________

So finally a clear view of a draft assembly. The yoke is the frame that encompasses the package which is the spring assembly. It is still sitting on the lift table. We can see the clevis arrangement on the left end where the coupler shank engages. In this particular package type the rear follower is part of what we might call the "spring chamber".

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So there we go. We hope that this makes it all clear for you! In coming days the drag box will be built up to as new dimensions, the draft assembly will be pre-loaded and the whole assembly put back in place. Meanwhile all those other things we get up to are still happening.